Flora of North America species comparison

Species 8 (2 in the flora).

J. Holub (1972b) argued that the correct name for this group, when segregated from Epilobium, should be Chamerion (Rafinesque) Rafinesque ex Holub. However, A. N. Sennikov (2011), using the more recent and clarified ICBN (Melbourne Code), correctly argued that the name of the segregated genus should be Chamaenerion, and that opinion is followed here.

All species of Chamaenerion tested to date have been self-compatible, although the strong protandry can result in low fertilization rates if there is a shortage of pollinators. Flowering is diurnal, with each flower generally remaining open for three to five or more days.

All eight species (nine taxa) of Chamaenerion are restricted to the northern hemisphere, and six of eight species occur only in Eurasia; Circaea is the only other genus of Onagraceae in which most species occur outside of the western hemisphere (D. E. Boufford 1982b). Chamaenerion is generally divided into two sections, each with four species (T. Tacik 1959; and, as Chamerion, J. Holub 1972b; W. L. Wagner et al. 2007). P. H. Raven (1976) and most others who treated this group as a section of Epilobium divided it into two corresponding subsections. Both species of Chamaenerion in North America are placed in sect. Chamaenerion (not treated formerly here), along with two species endemic to the Himalayan region, C. conspersum (Haussknecht) Kitamura and C. speciosum (Decaisne) Hoch & Gandhi (Chen C. J. et al. 1992); the other four species, all endemic in Eurasia, comprise sect. Rosmarinifolium Tacik.

Chamaenerion differs from Epilobium in leaves nearly always alternate, rarely subopposite or verticillate near stem base (versus opposite at least on proximal stem); absence of a floral tube (versus a distinct floral tube); slightly zygomorphic flowers with subequal stamens that are erect, later deflexed, and a style that is deflexed, later erect (versus actinomorphic flowers with erect stamens in two unequal series and erect style); and pollen shed in monads (versus pollen shed in tetrads, or monads in one species). Molecular analyses (D. A. Baum et al. 1994; R. A. Levin et al. 2004) provided strong support for Chamaenerion as a monophyletic group separate from Epilobium, and for sect. Chamaenerion (only C. angustifolium and C. latifolium sampled) as monophyletic.

The superfluous and illegitimate name Pyrogennema Lunell pertains here.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera 21, species 582 (16 genera, 246 species in the flora).

Onagroideae encompass the main lineage of the family, after the early branching of Ludwigia (R. A. Levin et al. 2003, 2004). This large and diverse lineage is distinguished by the presence of a floral tube beyond the apex of the ovary; sepals deciduous with the floral tube, petals, and stamens; pollen shed in monads (or tetrads in Chylismia sect. Lignothera and all but one species of Epilobium); ovular vascular system exclusively transseptal (R. H. Eyde 1981); ovule archesporium multicellular (H. Tobe and P. H. Raven 1996); and change in base chromosome number from x = 8 in Ludwigia to x = 10 or x = 11 at the base of Onagroideae (Raven 1979; Levin et al. 2003). Molecular work (Levin et al. 2003, 2004) substantially supports the traditional tribal classification (P. A. Munz 1965; Raven 1979, 1988); tribes are recognized to delimit major branches within the phylogeny of Onagroideae, where the branches comprise strongly supported monophyletic groups of one or more genera.

(Discussion copyrighted by Flora of North America; reprinted with permission.)